7-33.
What happens to the lubricating oil that
leaks past newly installed piston rings
into a cylinder?
1.
It drains into the sump
2.
It burns in the cylinder
3.
It collects on the piston crown
4.
It passes out of the cylinder into
the exhaust
7-34.
An unbalanced cylinder will cause which
of the following effects?
1.
It will gum up the combustion spaces
2.
It will score the cylinder wall
3.
It will corrode the piston crown
4.
It will overheat the engine
7-35.
Engine efficiency is measured by the
relationship between energy input and
what other factor?
1.
Temperature of exhaust
2.
Amount of fuel consumed
3.
Temperature of combustion
4.
Amount of power developed
7-36.
Compression ratio refers to the relation
between the volume of air above a piston
when it is at top dead center and what
other factor?
1.
The volume of air below the piston
when it is at top dead center
2.
The volume of air above the piston
when it is at bottom dead center
3.
The pressure of the air above the
piston when it is at top dead center
4.
The temperature of the air below the
piston when it is at bottom dead
center
7-37.
Why is the efficiency of the Otto cycle
less than that of the diesel cycle?
1.
Because the Otto cycle reaches a
higher temperature
2.
Because the Otto cycle has a lower
compression ratio
3.
Because the Otto cycle uses a
greater amount of air
4.
Because the Otto cycle uses a smaller
amount of air
7-38.
Assume that an engine has an indicated
horsepower of 1,600 and uses 400 pounds
of fuel per hour. If the fuel has a
value of 20,000 Btu per pound, what is
the indicated thermal efficiency of the
engine?
1.
40.9%
2.
49.4%
3.
50.9%
4.
53.2%
7-39.
If an engine consumes 70 pounds of fuel
in an hour and the fuel has a potential
energy of 20,000 Btu per pound, what is
the potential power of the engine? (Use
the factor of 2545 Btu per hr/hp.)
1.
36.4 hp
2.
55.0 hp
3.
363.6 hp
4.
550.1 hp
7-40.
The overall thermal efficiency of an
engine is 50 percent and the brake horse-
power is 1,450.00 Btu per hour.
What is
the value of the heat input of fuel?
1.
725,000 Btu per hr
2.
1,450,000 Btu per hr
3.
2,000,000 Btu per hr
4.
2,900,000 Btu per hr
7-41.
Which of the following factors has the
greatest effect on the mechanical
efficiency of an engine?
1.
Vaporization
2.
Corrosion
3.
Friction
4.
Combustion
7-4 2.
What is the relationship between the
amount of friction between the moving
parts of an engine and the speed of the
engine?
1.
Friction increases at high speeds
2.
Friction decreases at low speeds
3.
Friction remains constant throughout
the speed range
4.
Friction increases at low speeds and
decreases at high speeds
Information for questions 7-43 through
7-53: A 6-cylinder, single-acting,
2-stroke cycle, diesel engine has a mean
effective pressure of 104 psi per cylinder
when operating at full load and rated speed of
2,500 rpm. The stroke and cylinder bore are 5
inches and 4 inches, respectively. The engine's
frictional horsepower is 32 hp and does not
change with changes in load or speed. At 2,000
rpm, the brake horsepower for the engine is 166
hp.
45